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1. Ultrabroadband, few-cycle pulses directly from a Mamyshev fiber oscillator

   https://doi.org/10.1364/PRJ.8.000065  

   Ma, C; Khanolkar, A; Zang, Y; Chong, A (December 2019, Photonics research)

   While the performance of mode-locked fiber lasers has been improved significantly, the limited gain bandwidth restricts them from generating ultrashort pulses approaching a few cycles or even shorter. Here we present a novel method to achieve few-cycle pulses (∼5 cycles) with an ultrabroad spectrum (∼400 nm at −20 dB) from a Mamyshev oscillator configuration by inserting a highly nonlinear photonic crystal fiber and a dispersion delay line into the cavity. A dramatic intracavity spectral broadening can be stabilized by the unique nonlinear processes of a self-similar evolution as a nonlinear attractor in the gain fiber and a “perfect” saturable absorber action of the Mamyshev oscillator. To the best of our knowledge, this is the shortest pulse width and broadest spectrum directly generated from a fiber laser. 

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2. Complex Swift Hohenberg Equation (CSHE) Dissipative Soliton Fiber Laser

   Khanolka, A; Zang, Y; Chong, A (January 2021, Conference on Lasers and Electrooptics)

   null (Ed.)

   We report dissipative solitons of CSHE in a mode-locked fiber laser by employing a unique fiber filter which produces a fourth order spectral response. The laser generates moving, asymmetric pulses with a highly asymmetric spectrum. 

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3. Microcombs in fiber Fabry–Pérot cavities

   https://doi.org/10.1063/5.0177134  

   Musgrave, Jonathan; Huang, Shu-Wei; Nie, Mingming (December 2023, APL Photonics)

   Optical frequency combs, which consist of precisely controlled spectral lines covering a wide range, have played a crucial role in enabling numerous scientific advancements. Beyond the conventional approach that relies on mode-locked lasers, microcombs generated from microresonators pumped at a single frequency have arguably given rise to a new field within cavity nonlinear photonics, which has led to a robust exchange of ideas and research between theoretical, experimental, and technological aspects. Microcombs are extremely attractive in applications requiring a compact footprint, low cost, good energy efficiency, large comb spacing, and access to nonconventional spectral regions. The recently arising microcombs based on fiber Fabry–Pérot microresonators provide unique opportunities for ultralow noise and high-dimensional nonlinear optics. In this review, we comprehensively examine the recent progress of fiber Kerr microcombs and discuss how various phenomena in fibers can be utilized to enhance the microcomb performances that benefit a plethora of applications. 

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4. Fiber-based photon-pair generation: tutorial

   https://doi.org/10.1364/JOSAB.478008  

   Garay-Palmett, Karina; Kim, Dong Beom; Zhang, Yujie; Domínguez-Serna, Francisco A.; Lorenz, Virginia O.; U’Ren, Alfred B. (January 2023, Journal of the Optical Society of America B)

   The purpose of this tutorial paper is to present a broad overview of photon-pair generation through the spontaneous four wave mixing (SFWM) process in optical fibers. Progress in optical fiber technology means that today we have at our disposal a wide variety of types of fiber, which, together with the fact that SFWM uses two pump fields, implies a truly remarkable versatility in the resulting possible photon-pair properties. We discuss how the interplay of frequency, transverse mode, and polarization degrees of freedom—the first linked to the latter two through fiber dispersion—leads to interesting entanglement properties both in individual degrees of freedom and also permitting hybrid and hyper entanglement in combinations of degrees of freedom. This tutorial covers methods for photon-pair factorability, frequency tunability, and SFWM bandwidth control, the effect of frequency non-degenerate and counterpropagating pumps, as well as methods for characterizing photon pairs generated in optical fibers. 

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5. Realization of efficient 3D tapered waveguide-to-fiber couplers on a nanophotonic circuit

   https://doi.org/10.1364/OE.468738  

   Chang, Tzu-Han; Zhou, Xinchao; Tamura, Hikaru; Hung, Chen-Lung (January 2022, Optics Express)

   We report the realization of efficiently coupled 3D tapered waveguide-to-fiber couplers (TWCs) based on standard lithography techniques. The 3D TWC design is capable of achieving highly efficient flat-cleaved fiber to silicon nitride photonic waveguide coupling, with T  ≈ 95 % polarization-insensitive coupling efficiency, wide bandwidth, and good misalignment tolerance. Our fabricated 3D TWCs on a functional nanophotonic circuit achieve T  ≈ 85% coupling efficiency. Beyond applications in high-efficiency photon coupling, the demonstrated 3D lithography technique provides a complementary approach for mode field shaping and effective refractive index engineering, potentially useful for general applications in integrated photonic circuits. 

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